Taxol (registered trademark) (i) represented by the following formula (i): ##STR2## is a diterpenoid available by extraction from the bark of the Pacific yew tree, Taxus brevifolia, and was isolated and determined in structure for the first time in 1971 by Wall, et al. (J. Am. Chem. Soc., 93, 2325, 1971). It has been reported to exhibit high efficacy against ovarian cancer and breast cancer (Ann. int. Med. 111, 273, 1989).
Formulation of Taxol into an injection however requires a special solvent, as it is a compound sparingly soluble in water. Taxol is therefore accompanied by problems in that the production of an injection is difficult and side effects may be induced by a solvent.
A great deal of work has therefore been conducted in recent years with a view to developing a water-soluble derivative of Taxol (Nicolaou, et al., Nature, 364, 464, 1993). Under the current circumstances, however, no derivatives have been found yet to be equipped with satisfactory properties.
Accordingly, an object of the present invention is to provide a novel Taxol derivative having improved water solubility and high antitumor activities.